I plan on mounting my 16" spare tire (which is currently on a steel wheel) to a slightly used 16" GLX Vancouver rim. After mounting the spare tire to the new wheel, will it fit back into the trunk (thus allowing for the trunk floor to lie flat)?
Unless, they changed the size of the hole for the spare tire, it should fit. Early B5s used to get 5 rims/tires (4 on the car and 1 as the spare). You could actually rotate your tires using the spare in your rotation. I believe this was the case through early 2001 before VW used full sized steelies everywhere for spares.
I seem to remember stories about dealers taking the spares (GLX 16") out and replacing with a full size steelie and making profit on the spares.
I had my spare mounted on a slightly used GLX (Vancouver) wheel that I picked up through Ebay. I had to perform two minor modifications to the securing screw in order for: (1) the new wheel to fit securely, and (2) make the trunk floor lie mostly flat.
1. The new wheel is higher at the center of the wheel than the old 16" steelie; therefore, the first mod required buying a 5/16" 4" inch hex bolt (available at Home Depot) to replace the smaller hex bolt. This longer bolt allows the wheel to be reattached to the vehicle.
2. I also had to remove the cap that is on top of the securing screw to allow for the trunk floor to lie flat.
3. The final product looks like this -
In the end, the trunk floor has a slight rise where the top of the securing screw is located. I did not feel like taking a hacksaw to the mounting screw to make the trunk floor lie completely flat.